The 50mm does transmit more light if everything else is equal.However the quality and amount of lens coatings are just as important in light transmission.If you really want more light transmission you might consider a different scope from a different manufacturer such as the ziess conquest 3x9x40.It is made in America,is brighter ,yet can be mounted in lower mounts and the cost is about the same as a leupold vxiii.I use the swarovski 3x10x42 which is as bright as the leupold 3.5x10x50 as well as being lighter and more compact, but of course the cost is higher.For most situations though any quality scope with a 40mm lens will work fine.As far as service on the rifle is concerned,it is extremely unlikely that you will need any and since both rifles are made in japan the time required to do any work if it was necessary,would be similar.If you want to spend the extra money to say that you have a weatherby,that is your business,but you will still have the same rifle.